time-domain reflectometer (OTDR) measurements can be performed in-band
without service interruption.

Ratified as part of IEEE 802.3’s Ethernet
in the First Mile project, 1G EPON is a
1-Gbit/sec Ethernet passive optical network
standard. The 10G EPON standard was
also developed to support 10G/10G symmetric downstream and upstream speed.

Currently, the IEEE 802.3ca task force
is working on 25G/50G/100G EPON standards development. All EPON standards
are developed to be backward and forward compatible to support legacy service and new higher-speed service over
the same ODN.

Radio frequency over glass (RFoG) network design was developed by the Society
of Cable Telecommunications Engineers
(SCTE) under IPS 910 and later became
ANSI/SCTE 174.

Mainly deployed in North America,
backward compatibility with RFoG is
also required in some PON deployments
and upgrades.

Different PON systems can overlay on the same ODN with a CEx that
supports PON system forward/back-ward compatibility.

• Multiple OLTs of different generations
and service types can be overlaid over
the same fiber.

• In the downstream, signals from multiple OLTs are combined at CEx and
simultaneously sent to the ONT side.
Each ON T receives its signal with a
wavelength filter in the optical module. ON Ts also have wavelength
block filters (WBF) to block future
PON wavelengths.

• In the upstream, wavelengths from different ON Ts are separated at CEx and
WDM mux/demux to different OLTs.

PON system coexistence allows the reuse of existing fiber resources for fast deployment without a new investment; a
system upgrade to high-bandwidth services can be done by simply replacing or
adding OLT line cards.

POLAN deployment and migration

The step-by-step process of deploying aPOLAN is: 1) the first splitter is installedin the splitter cabinet next to the OLTrack; 2) the second splitter is installedon each floor for a dedicated distribu-tion group; 3) ON Ts in the work zone canbe standalone devices like WiFi routers,or conversion devices equipped with RJ45outlets to provide data services and PoE.

Upgrading a typical POLAN from
GPON to XGS-PON takes place in
four phases.

Phase 1: Deploy the ODN, install the
GPON OLT line cards and gradually add
GPON ON T devices at endpoints.

Phase 2: The GPON OLT line cards
reach full capacity; additional services
need to be added with new XGS-PON
equipment and end devices.

Phase 3: Install the XGS-PON OLT line
cards and add the CEx to the same ODN;
install the new XGS-PON ONT devices
with the legacy GPON OLT line cards and
some GPON ONT devices still in operation.

Phase 4: Add/replace with new XGS-PON ON T devices gradually until the system is fully upgraded. Some legacy ON T
devices will still be in operation for designated applications.

Deployment challenges of
in-building POLAN

When comparing POLAN to tradi-tional LAN technologies, it is not neces-sarily a “better” replacement solution forall the new access network deployment;

Upgrading from GPON to XSG-PON typically is carried out as a four-phase process. Once the network is completely
upgraded, some legacy ONT devices likely remain in operation for designated applications.